U.S. patent application number 12/847507 was filed with the patent office on 2010-11-18 for range-finding device.
This patent application is currently assigned to NIKON VISION CO., LTD. Invention is credited to Yukitsugu HATA.
Application Number | 20100290029 12/847507 |
Document ID | / |
Family ID | 41663350 |
Filed Date | 2010-11-18 |
United States Patent
Application |
20100290029 |
Kind Code |
A1 |
HATA; Yukitsugu |
November 18, 2010 |
RANGE-FINDING DEVICE
Abstract
A range-finding device includes: a light emitting unit that
continuously emits measurement light to be used for distance
measurement toward a measurement target object; a light-receiving
unit that receives reflected light reflected by the measurement
target object; a calculation unit that repeatedly calculates a
distance to the measurement target object over predetermined time
intervals by using the reflected light; a display unit at which an
update of the distance is displayed each time the distance is
calculated by the calculation unit; and a display update control
unit that prohibits the update of the distance on display at the
display unit and sustains the display of the previously calculated
distance at the display unit according to a change in the most
recently calculated distance calculated most recently by the
calculation unit relative to the previously calculated distance
having been calculated previously by the calculation unit.
Inventors: |
HATA; Yukitsugu;
(Hadano-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
NIKON VISION CO., LTD
TOKYO
JP
|
Family ID: |
41663350 |
Appl. No.: |
12/847507 |
Filed: |
July 30, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/JP2008/064145 |
Aug 6, 2008 |
|
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12847507 |
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Current U.S.
Class: |
356/5.01 |
Current CPC
Class: |
A63B 2220/805 20130101;
G01S 7/497 20130101; G01S 17/10 20130101; G01S 7/4873 20130101;
A63B 2220/20 20130101; A63B 2102/32 20151001; A63B 2071/065
20130101 |
Class at
Publication: |
356/5.01 |
International
Class: |
G01C 3/08 20060101
G01C003/08 |
Claims
1. A range-finding device, comprising: a light emitting unit that
continuously emits measurement light to be used for distance
measurement toward a measurement target object; a light-receiving
unit that receives reflected light reflected by the measurement
target object; a calculation unit that repeatedly calculates a
distance to the measurement target object over predetermined time
intervals by using the reflected light; a display unit at which an
update of the distance is displayed each time the distance is
calculated by the calculation unit; and a display update control
unit that prohibits the update of the distance on display at the
display unit and sustains the display of the previously calculated
distance at the display unit according to a change in the most
recently calculated distance calculated most recently by the
calculation unit relative to the previously calculated distance
having been calculated previously by the calculation unit.
2. A range-finding device according to claim 1, wherein: when
prohibiting the update of the distance on display at the display
unit, the display update control unit sustains the display of the
previously calculated distance at the display unit for a duration
of a predetermined holding time.
3. A range-finding device according to claim 2, wherein: once the
holding time elapses, a distance newly calculated by the
calculation unit is displayed at the display unit.
4. A range-finding device according to claim 1, further comprising:
a difference calculation unit that calculates a difference between
the distance most recently calculated by the calculation unit and
the previously calculated distance having been calculated
previously by the calculation unit, wherein: the display update
control unit prohibits the update of the distance on display at the
display unit based upon the difference as the change.
5. A range-finding device according to claim 4, further comprising:
a decision-making unit that makes a decision as to whether or not
the difference calculated by the difference calculation unit
exceeds a threshold value, wherein: when the decision-making unit
determines that the difference exceeds the threshold value, the
display update control unit prohibits the update of the distance on
display at the display unit and sustains the previously calculated
distance on display at the display unit.
6. A range-finding device according to claim 5, wherein: the
difference calculation unit calculates the difference by
subtracting the previously calculated distance from the most
recently calculated distance and also calculates the difference by
subtracting the most recently calculated distance from the
previously calculated distance.
7. A range-finding device according to claim 6, wherein: the
difference calculation unit includes a first difference calculation
unit that calculates the difference by subtracting the previously
calculated distance from the most recently calculated distance and
a second difference calculation unit that calculates the difference
by subtracting the most recently calculated distance from the
previously calculated distance; the decision-making unit includes a
first decision-making unit that makes a decision as to whether or
not the difference calculated by the first difference calculation
unit exceeds a first threshold value and a second decision-making
unit that makes a decision as to whether or not the difference
calculated by the second difference calculation unit exceeds a
second threshold value; and the range-finding device further
comprises a first operation member operated to select between a
first mode and a second mode, in the first mode the display update
control unit displaying the previously calculated distance at the
display unit when the difference calculated by the first difference
calculation unit exceeding the first threshold value, and in the
second mode the display update control unit displaying the
previously calculated distance at the display unit when the
difference calculated by the second difference calculation unit
exceeding the second threshold value.
8. A range-finding device according to claim 7, further comprising:
a second operation member operated to adjust a setting for the
first threshold value, the second threshold value or the holding
time.
9. A range-finding device according to claim 1, further comprising:
a viewing optical system through which the measurement target
object is viewed, wherein: a display is brought up at the display
unit so that at least an index indicating a measurement position
and the distance having been calculated are viewed within a visual
field containing the measurement target object.
Description
[0001] This application is a continuation of International
Application No. PCT/JP 2008/064145 filed Aug. 6, 2008
INCORPORATION BY REFERENCE
[0002] The disclosure of the following application is herein
incorporated by reference: International Application No. PCT/JP
2008/064145 filed Aug. 6, 2008
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates to a range-finding device that
measures the distance to a measurement target object.
[0005] 2. Description of Related Art
[0006] International Publication No. 02/0887722 discloses a laser
range-finding device that measures the distance to a measurement
target object by radiating pulse laser light or the like toward the
measurement target object and brings up the measurement results on
display at a distance display unit.
SUMMARY OF THE INVENTION
[0007] However, when the measurement of the distance to the
measurement target object is done continuously by the range-finding
device, it is difficult that user recognizes the measurement
distance to the measurement target object because the measurement
result display is continuously changed if the measurement target
objects have a specific shape or size.
[0008] According to the 1st aspect of the present invention, a
range-finding device comprises: a light emitting unit that
continuously emits measurement light to be used for distance
measurement toward a measurement target object; a light-receiving
unit that receives reflected light reflected by the measurement
target object; a calculation unit that repeatedly calculates a
distance to the measurement target object over predetermined time
intervals by using the reflected light; a display unit at which an
update of the distance is displayed each time the distance is
calculated by the calculation unit; and a display update control
unit that prohibits the update of the distance on display at the
display unit and sustains the display of the previously calculated
distance at the display unit according to a change in the most
recently calculated distance calculated most recently by the
calculation unit relative to the previously calculated distance
having been calculated previously by the calculation unit.
[0009] According to the 2nd aspect of the present invention, it is
preferred that in the range-finding device according to the 1st
aspect, when prohibiting the update of the distance on display at
the display unit, the display update control unit sustains the
display of the previously calculated distance at the display unit
for a duration of a predetermined holding time.
[0010] According to the 3rd aspect of the present invention, it is
preferred that in the range-finding device according to the 2nd
aspect, once the holding time elapses, a distance newly calculated
by the calculation unit is displayed at the display unit.
[0011] According to the 4th aspect of the present invention, it is
preferred that the range-finding device according to the 1st aspect
further comprises: a difference calculation unit that calculates a
difference between the distance most recently calculated by the
calculation unit and the previously calculated distance having been
calculated previously by the calculation unit, and in the
range-finding device the display update control unit prohibits the
update of the distance on display at the display unit based upon
the difference as the change.
[0012] According to the 5th aspect of the present invention, it is
preferred that the range-finding device according to the 4th aspect
further comprises: a decision-making unit that makes a decision as
to whether or not the difference calculated by the difference
calculation unit exceeds a threshold value, and in the
range-finding device when the decision-making unit determines that
the difference exceeds the threshold value, the display update
control unit prohibits the update of the distance on display at the
display unit and sustains the previously calculated distance on
display at the display unit.
[0013] According to the 6th aspect of the present invention, it is
preferred that in the range-finding device according to the 5th
aspect, the difference calculation unit calculates the difference
by subtracting the previously calculated distance from the most
recently calculated distance and also calculates the difference by
subtracting the most recently calculated distance from the
previously calculated distance.
[0014] According to the 7th aspect of the present invention, it is
preferred that in the range-finding device according to the 6th
aspect, the difference calculation unit includes a first difference
calculation unit that calculates the difference by subtracting the
previously calculated distance from the most recently calculated
distance and a second difference calculation unit that calculates
the difference by subtracting the most recently calculated distance
from the previously calculated distance; the decision-making unit
includes a first decision-making unit that makes a decision as to
whether or not the difference calculated by the first difference
calculation unit exceeds a first threshold value and a second
decision-making unit that makes a decision as to whether or not the
difference calculated by the second difference calculation unit
exceeds a second threshold value; and the range-finding device
further comprises a first operation member operated to select
between a first mode and a second mode, in the first mode the
display update control unit displaying the previously calculated
distance at the display unit when the difference calculated by the
first difference calculation unit exceeding the first threshold
value, and in the second mode the display update control unit
displaying the previously calculated distance at the display unit
when the difference calculated by the second difference calculation
unit exceeding the second threshold value.
[0015] According to the 8th aspect of the present invention, it is
preferred that the range-finding device according to the 7th aspect
further comprises: a second operation member operated to adjust a
setting for the first threshold value, the second threshold value
or the holding time.
[0016] According to the 9th aspect of the present invention, it is
preferred that the range-finding device according to the 1st aspect
further comprises: a viewing optical system through which the
measurement target object is viewed, and in the range-finding
device a display is brought up at the display unit so that at least
an index indicating a measurement position and the distance having
been calculated are viewed within a visual field containing the
measurement target object.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 provides an external view of the range-finding device
achieved in an embodiment of the present invention
[0018] FIG. 2 is a block diagram showing the internal structure of
the range-finding device achieved in the embodiment
[0019] FIGS. 3A.about.3C each present an example of a measured
distance frequency distribution
[0020] FIG. 4 presents an example of a measurement target object
that can be visually checked by the user via the eyepiece unit
4
[0021] FIG. 5 shows the relationship between the measurement
results obtained through distance measurement and the display
update
[0022] FIGS. 6A.about.6H each present an example of a display that
may be brought up to provide distance measurement results, with
FIG. 6A presenting an example of a display providing the first
measurement results, FIG. 6B presenting an example of a display
providing the second measurement results, FIG. 6C presenting an
example of a display providing the third measurement results, FIG.
6D presenting an example of a display providing the fourth
measurement results, FIG. 6E presenting an example of a display
providing the fifth measurement results, FIG. 6F presenting an
example of a display providing the sixth measurement results, FIG.
6G presenting an example of a display providing the seventh
measurement results and FIG. 6H presenting an example of a display
providing the eighth measurement results
[0023] FIG. 7 presents a flowchart of the operation executed in the
range-finding device in the embodiment
[0024] FIG. 8 presents a flowchart of the operation executed in the
range-finding device in the embodiment, and
[0025] FIG. 9 presents a flowchart of the operation executed in the
range-finding device in the embodiment.
DESCRIPTION OF PREFERRED EMBODIMENT
[0026] The following is a description of the range-finding device
achieved in an embodiment of the present invention. The
range-finding device in the embodiment measures the distance to a
measurement target object by measuring the length of time to elapse
(time lag) between a time point at which measurement light is
emitted and a time point at which light reflected off the
measurement target object is returned.
[0027] As the external view provided in FIG. 1 shows, the
range-finding device 1 includes an objective lens 2, a
light-receiving lens 3, an eyepiece unit 4, a mode button 5 and a
power button 6. The objective lens 2 and the light-receiving lens 3
are disposed at the front surface of the range-finding device 1.
Light having traveled from the measurement target object and
entered the objective lens 2 is guided via the objective lens 2 to
the eyepiece unit 4 disposed on the rear side of the range-finding
device 1. While measuring the distance to the measurement target
object, the user is able to observe the measurement target object
via the eyepiece unit 4. In addition, pulse laser light having
originated at a laser light emitter to be detailed later, is used
as measurement light in the distance measurement after it departs
the objective lens 2. The measurement light reflected at the
measurement target object (reflected light) is then received via
the light-receiving lens 3 at a light-receiving sensor to be
described later.
[0028] The mode button 5 and the power button 6 are disposed at the
top of the casing of the range-finding device, at positions at
which the user holding the range-finding device 1 in one hand is
able to operate the buttons with ease. The mode button 5 is an
operation member operated by the user in order to switch between a
short distance priority mode and a long distance priority mode as
detailed later, to select either a continuous measurement or a
one-time measurement, or to select/reset various other settings.
The power button 6 is an operation member operated by the user to
turn on/off power, start range-finding operation, confirm a setting
having been selected via the mode button 5 or the like.
[0029] As shown in the internal structure block diagram presented
in FIG. 2, the range-finding device 1 includes a laser light
emitter 11, a drive circuit 12, a light emission detection circuit
13, a control circuit 14, a built-in display unit 15, a
light-receiving sensor 16, an amplifier circuit 17, a threshold
value setting circuit 18, a binary coding circuit 19, an FPGA
(field programmable gate array) circuit 20 and an oscillator 21.
The laser light emitter 11 is a light emitting element such as a
laser diode that emits semiconductor laser light. The drive circuit
12 is a pulse generation circuit that outputs a drive pulse to the
laser light emitter 11 a predetermined number of times (e.g., 550
times) over a predetermined measurement cycle, which goes on for a
predetermined length of time (e.g., 12.5 ns) based upon a signal
provided from the control circuit 14. As a result, the laser light
to be used as the measurement light is emitted 550 times for each
measurement session. The light emission detection circuit 13
outputs to the FPGA circuit 20 a signal indicating the timing with
which the laser light has been emitted each time the laser light
emitter 11 emits laser light.
[0030] The control circuit 14, which is an arithmetic operation
circuit equipped with a CPU, a ROM, a RAM and the like (not shown),
controls the various structural elements constituting the
range-finding device 1 and executes various types of data
processing. In addition, based upon the measurement light frequency
distribution (histogram) input thereto from the FPGA circuit 20 to
be detailed later, the control circuit 14 calculates measurement
results (indicating the measured distance) for each range-finding
session. The control circuit 14 drives the built-in display unit 15
via an LCD driver 151 installed in the FPGA circuit 20 so as to
bring up on display the measurement results indicating the measured
distance. At the built-in display unit 15, constituted with a
liquid crystal display unit or the like and disposed between the
objective lens 2 and the eyepiece unit 4, the measured distance or
a reticle is displayed. Thus, the measured distance or the reticle
displayed at the built-in display unit 15, is positioned within the
same visual field as that in which the image of the measurement
target object, observed via the eyepiece unit 4, is present and the
user is able to view the measured distance or the reticle together
with the target object image in the same field. It is to be noted
that a liquid crystal display unit or the like may be disposed at
the exterior of the body of the laser range-finding device 1 in
place of the built-in display unit 15.
[0031] The light-receiving sensor 16, which is a photoelectric
conversion element such as a photodiode, receives the reflected
light having traveled back from the measurement target object,
converts the reflected light to an electrical signal corresponding
to the intensity of the received reflected light and outputs the
electrical signal to the amplifier circuit 17. The amplifier
circuit 17 executes amplification processing and the like on the
signal input thereto and outputs the signal having undergone the
amplification processing and the like to the binary coding circuit
19.
[0032] The binary coding circuit 19 is a comparator that compares
the signal indicating the intensity of the reflected light, having
been input thereto from the amplifier circuit 17, with an intensity
decision-making threshold value input from the threshold value
setting circuit 18. Consequently, a signal indicating reflected
light with an intensity level exceeding the intensity
decision-making threshold value, i.e., a signal indicating
reflected light exceeding the noise component, is output to the
FPGA circuit 20.
[0033] The FPGA circuit 20 is a gate array capable into which a
logic circuit may be written. The FPGA circuit 20 samples the
reflected light at each cycle of a timing signal output from the
oscillator 21. Then, based upon the signals input thereto from the
light emission detection circuit 13 and the binary coding circuit
19, the FPGA circuit 20 calculates the distance to the measurement
target object. Namely, the length of time having elapsed until the
measurement light emitted from the laser light emitter 11 and
reflected at the measurement target object is received at the
light-receiving sensor 16, is converted to a value indicating the
distance based upon the speed with which the laser light is
propagated through the space.
[0034] Based upon the measured distances calculated as described
above in correspondence to the 550 shots of laser light, the FPGA
circuit 20 creates a frequency distribution (histogram) through a
method of the known art. FIGS. 3A.about.3C each present an example
of a histogram that may be created by the FPGA circuit. The FPGA
circuit 20 then stores the histogram into a specific memory within
the FPGA circuit 20 and also outputs the histogram to the control
circuit 14. The control circuit 14 calculates the measured distance
by using the histogram input thereto. The following is an
explanation of measured distance calculation, given in reference to
the histograms presented in FIGS. 3A.about.3C.
[0035] The histogram in FIG. 3A indicates greater frequencies in
correspondence to distances X and Y. Under these circumstances, the
control circuit 14 determines a distance corresponding to the
frequency exceeding a decision-making threshold value P1 indicated
by the one-point chain line in FIG. 3A to be the measured distance.
The decision-making threshold value P1 is set so that it changes in
correspondence to the distance, i.e., so that its value becomes
smaller as the distance to the measurement target object increases.
In the example presented in FIG. 3A, the distance X is determined
to be the measured distance. It is to be noted that if there is no
frequency exceeding the decision-making threshold value P1, the
control circuit 14 determines the measured distance by using a
decision-making threshold value P2 which also changes in
correspondence to the distance, as indicated by the two-point chain
line in FIG. 3B. A value that is invariably smaller than the
decision-making threshold value P1 is assumed for the
decision-making threshold value P2.
[0036] FIG. 3C shows a plurality of distances corresponding to
frequencies exceeding the decision-making threshold value P1, i.e.,
the frequencies corresponding to the distance X and the distance Y
both exceed the decision-making threshold value P1. In this
situation, the control circuit 14 makes a decision as to whether
the user has selected the short distance priority mode or the long
distance priority mode. Then, if the short distance priority mode
is currently set, the control circuit 14 determines the distance X
to be the measured distance, whereas if the long distance priority
mode is currently set, the control circuit 14 determines the
distance Y to be the measured distance.
[0037] The display control executed to display the measurement
results (measured distance) in conjunction with the one-time
measurement setting and the display control executed to display the
measurement results in conjunction with the continuous measurement
setting are now individually described. It is to be noted that
while an explanation is given on an example in which the continuous
measurement setting is selected by operating the mode button 5, the
continuous measurement operation may instead start as the power
button 6 is held down for a predetermined length of time or more
(prolonged depression). In addition, the following explanation is
given by assuming that the short distance priority mode is
currently set.
[0038] One-Time Measurement
[0039] In a one-time measurement operation, the control circuit 14
calculates the measured distance by executing distance measurement
once, as described above, in response to a measurement start
instruction signal input thereto from a power switch 6a
corresponding to the power botton 6 as the power button 6 is
operated. The control circuit 14 then brings up the measured
distance on display at the built-in display unit 15 by controlling
the LCD driver 151.
[0040] Continuous Measurement
[0041] In a continuous measurement operation, the control circuit
14 executes distance measurement successively over predetermined
time intervals, e.g., 0.2-sec intervals over a duration of for
instance, 8 seconds in response to the measurement start
instruction signal input thereto from the power switch 6a. Each
time the distance measurement results become available, the control
circuit 14 updates the measurement result display at the built-in
display unit 15 by controlling the LCD driver 151. In other words,
the measured distance display at the built-in display unit 15 will
normally be updated every 0.2 sec.
[0042] If the change in the current measurement results relative to
the previous measurement results, i.e., the difference between the
current measurement results and the previous measurement results,
satisfies a specific condition (1) below, the control circuit 14
prohibits the update of the measurement result display and instead
keeps the same measurement results on display during a specific
length of holding time, e.g., 0.8 seconds.
[0043] In other words, the control circuit 14 does not display four
consecutive sets of measurement results at the built-in display
unit 15. It is to be noted that the length of the holding time can
be adjusted by the user by operating the mode button 5.
B-A.gtoreq.a (1)
[0044] A, B and a in the expression presented above respectively
represent the previous measured distance, the current measured
distance and a reference distance.
[0045] Once the 0.8-sec holding time elapses, the control circuit
14 displays the measured distance indicated by the newly acquired
measurement results at the built-in display unit 15. The control
executed by the control circuit 14 is now explained in further
detail in reference to FIGS. 4.about.6H.
[0046] FIG. 4 presents an example of a measurement target object
visually checked by the user via the eyepiece unit 4 during the
distance measurement. FIG. 4 shows a pin flag PF on a golf course,
the distance to which is being measured, with trees present beyond
the flag PF further away from the user. In addition, a reticle
index R in FIG. 4 indicates the position at which the distance
measurement is executed. When the measurement target is a thin
object such as the pin flag PF, the reticle index R cannot easily
be aligned with the measurement target object. Accordingly, the
user often performs continuous measurement (scan) by moving the
range-finding device 1 in tiny increments from a point near the pin
flag PF (a point on the left side or the right side of the pin flag
PF) to fix on the pin flag PF. Thus, the following description is
provided by assuming that the continuous measurement is executed as
the reticle index R shifts along the direction indicated by the
dotted-line arrow Q in FIG. 4. In addition, the following
description is given by assuming that the reference distance a in
conditional expression (1) is set to 5 yd. The reference distance a
can be adjusted by the user by operating the mode button 5.
[0047] FIG. 5 shows the relationship between the measurement
results obtained through the continuous measurement in the short
distance priority mode and the display update. As described
earlier, the control circuit 14 calculates a first measured
distance D1 based upon the histogram input thereto from the FPGA
circuit 20. The control circuit 14 then controls the LCD driver 151
so as to display the calculated measured distance D1 (190 yd) at
the built-in display unit 15. The user is thus able to view the
measured distance (190 yd) in the same visual field where the image
of the measurement target object, i.e., the pin flag PF, is
present, as shown in the example for the first display presented in
FIG. 6A. The control circuit 14 also stores measured distance data
d1 corresponding to the first measured distance D1 having been
input into a specific memory (not shown) within the control circuit
14.
[0048] When the predetermined length of time, i.e., 0.2 sec,
elapses following the end of the first measurement, the control
circuit 14 takes in the histogram created by the FPGA circuit 20 by
executing the second measurement. The control circuit 14 then
calculates a second measured distance D2 (180 yd). The control
circuit 14 calculates the difference between the measured distance
data d2 corresponding to the measured distance D2 and the first
measured distance data d1 stored in the memory and makes a decision
as to whether or not the difference indicated by the calculation
results satisfies the condition (1). The difference obtained by
subtracting the first measured distance (190 yd) from the second
measured distance (180 yd) is (-10 yd) and therefore, the condition
(1) is not satisfied. In this situation, the control circuit 14
controls the LCD driver 151 so as to bring up the measured distance
D2 (180 yd) corresponding to the measured distance data d2 up on
display at the built-in display unit 15. Namely, the display at the
built-in display unit 15 is switched and the user is able to view
the measured distance (180 yd) in the same visual field where the
image of the pin flag PF is present, as shown in the example of the
second display presented in FIG. 6B. In addition, the control
circuit 14 stores the measured distance data d2 by overwriting the
memory.
[0049] Next, the control circuit 14 calculates a third measured
distance D3 (179 yd) through a similar process. The difference
obtained by subtracting the second measured distance D2 (180 yd)
from the third measured distance D3 (179 yd) is (-1 yd) and
therefore, the condition (1) is not satisfied. Accordingly, the
control circuit 14 switches the display at the built-in display
unit 15 and brings up the measured distance D3 (179 yd)
corresponding to the measured distance data d3 on display. An
example of display that may be brought up in this situation is
presented in FIG. 6C.
[0050] After finishing the third measurement, the control circuit
14 calculates a fourth measured distance D4 (187 yd) through a
similar process, calculates the difference between measured
distance data d4 corresponding to the measured distance D4 and the
third measured distance data d3 stored in the memory, and makes a
decision as to whether or not the difference indicated by the
calculation results satisfies the condition (1). The difference
calculated by subtracting the third measured distance (179 yd) from
the fourth measured distance (187 yd) is 8 yd and, therefore, the
condition (1) is satisfied. Under these circumstances, the control
circuit 14 keeps the measured distance D3 (179 yd) corresponding to
the measured distance data d3 on display at the built-in display
unit 15. Namely, the control circuit 14 prohibits any alteration in
the display at the built-in display unit 15. As a result, the
measured distance (179 yd) continues to be viewed by the user in
the same visual field where the image of the pin flag PF is
present, as shown in the example for the fourth display presented
in FIG. 6D. At this time, the control circuit 14 starts up a hold
counter. The hold encounter is engaged in operation to count the
number of times the distance measurement is executed while the
display alteration is prohibited.
[0051] Subsequently, the control circuit 14 sustains the
prohibition against any alteration of the measured distance display
at the built-in display unit 15 even as measured distances are
calculated in correspondence to the fifth through seventh
measurements. As a result, while the distance is measured four
times through the fourth through seventh measurements, i.e., until
the holding time (0.8 sec) elapses, the measured distance D3 (179
yd) corresponding to the measured distance data d3 remains on
display at the built-in display unit 15. Thus, the same measured
distance (179 yd), still in the same visual field where the image
of the pin flag PF is present, continues to be viewed by the user,
as shown in the examples of the fourth through seventh displays
presented in FIGS. 6D through 6G. Each time a histogram is input
from the FPGA circuit 20 and a measured distance is calculated
while the prohibition against alteration of the measured distance
display at the built-in display unit 15 is in effect, the control
circuit 14 increments the hold counter.
[0052] Once the count at the hold counter reaches 4 and the control
circuit 14 calculates the measured distance based upon the
histogram subsequently input from the FPGA 20 (an eighth measured
distance D8 in the example presented in FIG. 5), the control
circuit 14 controls the built-in display unit 15 so as to display
the measured distance D8 (190 yd) corresponding to measured
distance data d8. As a result, the user is able to view the
measured distance (190 yd), indicated by the most recent
measurement results, in the same visual field where the image of
the pin flag PF is present, as shown in the example of the eighth
display presented in FIG. 6H. At this time, the control circuit 14
stores the eighth measured distance data d8 into the specific
memory mentioned earlier and subsequently repeatedly executes the
processing described above.
[0053] While an explanation is given above by assuming that the
user has selected the short distance priority mode, the control
circuit 14 executes similar processing when the long distance
priority mode is set. It is to be noted, however, that the control
circuit 14 prohibits the measurement result display update when the
following condition (2) is satisfied and leaves the same
measurement results on display over the 0.8-sec period.
A-B.gtoreq.b (2)
[0054] A, B and b in the expression presented above respectively
represent the previous measured distance, the current measured
distance and a reference distance.
[0055] It is to be noted that while an explanation is given above
by assuming that the distance to the target object can be
calculated, the control circuit 14 will not be able to calculate
the measured distance if the measurement target object is set
against, for instance, the sky, and the measurement light is not
reflected off the target object, or if the measurement target
object is positioned too far away, beyond the maximum
measurement-enabled range. In such a case, the control circuit 14
controls the built-in display unit 15 so as to indicate that the
distance measurement cannot be executed, e.g., "---", instead of
displaying the measured distance.
[0056] In reference to the flowcharts presented in FIGS. 7.about.9,
the operation executed at the range-finding device 1 is described.
The processing in FIGS. 7.about.9 is executed by the control
circuit 14 based upon a program. The program, stored in a memory
(not shown) is started up as the power button 6 is operated to
shift from the power OFF state to the power ON state.
[0057] In step S1, the various units constituting the range-finding
device 1 are started up and undergo error checks before the
operation proceeds to step S2. In step S2, a decision is made as to
whether or not the short distance priority mode is currently set.
If the short distance priority mode has been selected, an
affirmative decision is made in step S2 and the operation proceeds
to step S3. In step S3, various phases of the processing in the
short distance priority mode are executed and then the operation
proceeds to step S5. It is to be noted that the processing executed
in step S3 in the short distance priority mode is to be described
in detail later, in reference to FIG. 8. If, on the other hand, the
long distance priority mode has been selected, a negative decision
is made in step S2 and the operation proceeds to step S4. In step
S4, various phases of the processing in the long distance priority
mode are executed and then the operation proceeds to step S5. It is
to be noted that the processing executed in step S4 in the long
distance priority mode is to be described in detail later, in
reference to FIG. 9.
[0058] In step S5, a decision is made as to whether or not the user
has performed any of various operations. If a signal originating
from a mode switch 5a or the power switch 6a has been input, an
affirmative decision is made in step S5 and the operation returns
to step S2. If no signal from either the mode switch 5a or the
power switch 6a has been input, a negative decision is made in step
S5 and the operation proceeds to step S6. At this time, a timer
(not shown) is started up to start counting the length of time
during which no signal is input. In step S6, a decision is made as
to whether or not 8 seconds have elapsed after starting the time
count on the timer in step S5. If 8 seconds have elapsed, an
affirmative decision is made in step S6 and the processing ends.
If, on the other hand, 8 seconds have not elapsed, a negative
decision is made in step S6 and the operation returns to step
S5.
[0059] In reference to FIG. 8, the short distance priority mode
processing executed in step S3 is described.
[0060] In step S201, a decision is made as to whether or not a
measurement start instruction has been issued by the user. If a
measurement start instruction signal has been input from the power
switch 6a, an affirmative decision is made in step S201 and the
operation proceeds to step S202, At this time, the timer (not
shown) is started up for a time count. If no measurement start
instruction signal has been input, a negative decision is made in
step S201 and the decision-making processing described above is
repeatedly executed.
[0061] In step S202, the laser light emitter 11 is caused to emit
light via the drive circuit 12, before the operation proceeds to
step S203. In step S203, the measured distance calculation
described earlier is executed by using the measurement light
received at the light-receiving sensor 16, and then the operation
proceeds to step S204. In step S204, a decision is made as to
whether or not the hold counter i indicates a value equal to or
greater than 1. An affirmative decision is made in step S204 if the
count value indicated at the hold counter i is equal to or greater
than 1 and the operation proceeds to step S205. If the count value
indicated at the hold counter i is 0, a negative decision is made
in step S204 and the operation proceeds to step S210 to be detailed
later.
[0062] In step S205, a decision is made as to whether or not the
count value indicated at the hold counter i is 4. If the count
value at the hold counter i is 4, an affirmative decision is made
in step S205 and the operation proceeds to step S206. If, on the
other hand, the count value at the hold counter i is not 4, a
negative decision is made in step S205, and the measured distance
calculated in step S203 is brought up on display at the built-in
display unit 15 before the operation proceeds to step S207. In step
S207, the count value at the hold counter i is cleared to 0 and
then the operation proceeds to step S214.
[0063] If a negative decision is made in step S205, the operation
proceeds to step S208 to sustain the current measured distance
display at the built-in display unit 15 before proceeding to step
S209. In step S209, the count value at the hold counter i is
incremented by 1 before the operation proceeds to step S214.
[0064] If a negative decision is made in step S204, the operation
proceeds to step S210 to make a decision as to whether or not the
relationship between the measured distance calculated through the
previous distance measurement and the measured distance calculated
through the current distance measurement satisfies the condition
(1). If the condition (1) is satisfied, i.e., if the measured
distance calculated through the current distance measurement is
greater than the measured distance indicated by the previous
measurement results by 5 yd or more, an affirmative decision is
made in step S210 and the operation proceeds to step S211. If the
condition (1) is not satisfied, a negative decision is made in step
S210 and the operation proceeds to step S213.
[0065] In step S211, the measured distance display currently up at
the built-in display unit 15 is sustained and then the operation
proceeds to step S212. In step S212, the count value at the hold
counter i is set to 1 before the operation proceeds to step
S214.
[0066] If a negative decision is made in step S210, the operation
proceeds to step S213 to bring up the measured distance indicated
by the current measurement results having been calculated in step
S203 on display at the built-in display unit 15, before the
operation proceeds to step S214. In step S214, a decision is made
as to whether or not 8 seconds have elapsed after starting the time
count on the timer in step S201. If 8 seconds have elapsed, an
affirmative decision is made in step S214 and the operation
proceeds to step S215. If 8 seconds have not elapsed, a negative
decision is made in step S214 and the operation returns to step
S202. In step S215, the measurement light emission at the laser
light emitter 11 is terminated via the drive circuit 12 to end the
short distance priority mode processing.
[0067] In reference to FIG. 9, the long distance priority mode
processing executed in step S4 is described.
[0068] The processing executed in step S301 (decision-making with
regard to whether or not a measurement start instruction has been
issued) through step S309 (incrementing the count value at the hold
counter i) is identical to that executed in step S201
(decision-making with regard to whether or not a measurement start
instruction has been issued) through step S209 (incrementing the
count value at the hold counter i) in FIG. 8. In step S310, a
decision is made as to whether or not the difference between the
previous measured distance and the current measured distance
satisfies the condition (2). If the condition (2) is satisfied, an
affirmative decision is made in step S310 and the operation
proceeds to step S311. If the condition (2) is not satisfied, a
negative decision is made in step S310 and the operation proceeds
to step S313. The processing executed in step S311 (sustaining the
previous measurement result display) through step S315 (ending the
measurement) is identical to the processing executed in step S211
(sustaining the previous measurement result display) through step
S215 (ending the measurement) in FIG. 8.
[0069] The following advantages are achieved through the embodiment
described above.
[0070] (1) The control circuit 14, engaged in a continuous
measurement operation, repeatedly calculates the distance to the
measurement target object every 0.2 seconds and each time the
distance is calculated, it updates the distance display at the
built-in display unit 15. However, the control circuit 14 prohibits
the update of the distance display at the built-in display unit 15
and sustains the display of the previously calculated distance at
the built-in display unit 15 based upon the difference between the
current distance calculated most recently and the previously
calculated distance. As a result, once a desirable distance to the
measurement target object is brought up on display at the built-in
display unit 15 during the continuous measurement (scan) operation,
the display remains unaltered in the event that the distance to an
undesired measurement target object is calculated. Accordingly, the
user is able to ascertain the distance to the desired measurement
target object with ease and better user convenience is assured.
[0071] (2) The control circuit 14 prohibits the update on the
distance display at the built-in display unit 15 by sustaining the
display of the previously calculated distance at the built-in
display unit 15 over a specific length of holding time lasting 0.8
seconds. This feature differentiates the present invention from the
prior art, in which the distance display at the built-in display
unit 15 is updated each time the measured distance is calculated.
Since the user is no longer required to memorize the distance to
the desired measurement target object, which has been on display
only briefly (0.2 sec), better user convenience is assured.
[0072] (3) Once the holding time is up, the control circuit 14
brings up the newly calculated distance on display at the built-in
display unit 15. Since the distance display update resumes after
the holding time elapses, a situation in which the range-finding
device 1 is erroneously thought to be malfunctioning or to have
become frozen never occurs.
[0073] (4) The control circuit 14 makes a decision as to whether or
not the calculated difference exceeds the threshold value a and if
the difference is judged to exceed the threshold value a, the
control circuit prohibits the distance display update at the
built-in display unit 15 to sustain the display of the previously
calculated distance at the built-in display unit 15. In other
words, as long as the difference does not exceed the threshold
value a, the distance display is updated. Thus, since the distance
display update is not prohibited too frequently, to result in an
undesired measured distance display being held on display at the
display unit, the user is prevented from confusing the wrong
distance with the correct measured distance.
[0074] (5) In the short distance priority mode, the control circuit
14 prohibits the distance display update at the built-in display
unit 15 and sustains the display of the previously calculated
distance at the built-in display unit 15 if the calculated
difference satisfies the condition (1) as explained earlier. In the
long distance priority mode, the control circuit 14 prohibits the
distance display update at the built-in display unit 15 and
sustains the display of the previously calculated distance at the
built-in display unit 15 if the calculated difference satisfies the
condition (2) as explained earlier. Namely, the criterion based
upon which the display update is prohibited can be switched in
correspondence to a specific distance measurement target object,
e.g., a pin flag on a golf course with very few obstacles present
between the range-finding device and the target or an animal in the
woods with a number of obstacles present between the range-finding
device and the target object. As a result, the measured distance
display is sustained in an optimal manner in correspondence to the
conditions of the specific measurement target object to assure
better user convenience.
[0075] (6) The user is able to adjust the threshold values a and b
and the length of the holding time by operating the mode button 5
in the menu screen. Thus, the criterion for prohibiting the display
update or the length of time over which the measured distance
display is sustained can be adjusted in correspondence to the
conditions of the measurement target object, making it possible to
sustain the measured distance display in a manner optimal for the
specific operating conditions, thereby improving the user
convenience.
[0076] (7) As shown in FIGS. 4 and 6, at least the reticle R
indicating measurement position and the measured distance can be
viewed by the user via the eyepiece unit 4 in the same visual field
where the image of the measurement target is present. This helps
the user to easily ascertain that the measured distance on display
indicates the distance to the measurement target object and thus
improves the user convenience.
[0077] The embodiment described above allows for the following
variations.
[0078] (1) Instead of measuring the length of the holding time via
the hold counter i, the length of time elapsing after the
prohibition of the measured distance display update takes effect
may be measured on a timer or the like.
[0079] (2) Instead of both the short distance priority mode and the
long distance priority mode, only either the short distance
priority mode or the long distance priority mode may be available
at the range-finding device 1.
[0080] (3) Instead of designating the difference between the most
recently calculated measured distance and the previously calculated
measured distance as the change to be scrutinized based upon the
specific criterion, the decision as to whether or not the specific
condition is satisfied may be made based upon the ratio of the most
recently calculated measured distance and the previously calculated
measured distance or based upon whether or not one measured
distance is greater than the other.
[0081] While the invention has been particularly shown and
described with respect to a preferred embodiment thereof by
referring to the attached drawings, the present invention is not
limited to the example and it will be understood by those skilled
in the art that various changes in form and detail may be made
therein without departing from the spirit, scope and teaching of
the invention.
* * * * *